Study On The Impact Of Temperature And Moisture Contents On Transformer Oil-paper Insulation Ageing Characteristics And Life

Power transformer is the core equipment of power system, its safe and reliable operation have an important impact on power network. Transformer oil-paper insulation performance has a direct decision of the transformer operating conditions. The influence factors about ageing characteristics and lifetime evalutions of oil-paper insulation are attracting more and more attention. In view of the life of the paper determines the life of the transformer, and the main form of paper cellulose degradation in oil is hydrolysis under heat, expore the impact of temperature and moisture contents on oil-paper insulation ageing characteristics and propose more suitable method for insulation life prediction is a important works in practice.In this paper, 25# transformer oil, ordinary kraft paper and copper are used as raw material, simulate the actual transformer production process, making the oil-paper samples with initial moisture contents of 1%, 3%, 5%, and let samples with different initial moisture contents ageing at 90℃, 110℃and 130℃. Detailed analyse the polymerization degree of insulation paper, moisture contents of paper and oil, fufural contents in oil and oil acidity varying with time for different initial mositure oil-paper samples at different temperature, and also analyse the relationship between above-mentioned ageing indicators and ageing status of oil-paper insulation. On this basis, cellulose degradation kinetic model in terms of the DP loss accumulation applied to explain the polymerization degree of insulation paper variation during ageing under different temperature and moisture contents. And established the oil-paper insulation life prediction model based on time-temperature superposition theory and DP loss accumulation kinetic model.The main conclusions are as follows:①The higher temperature, the more moisture contents, the faster decline in degree of polymerization, oil-paper insulation ageing more rapidly. In addition, temperature and moisture contents have synergistic effect in oil-paper ageing.②Both higher temperature and more moisture contents increase the rate of formation of furfurals and acids. But water can affect the distribution ratio of furfurals and acids in oil-paper system, therefore, insulation's water contents must be take into account when use furfural and acid in oil to assess the ageing state of oil-paper insulation.③The insulation ageing rate is not constant, but decreases with ageing time. It turns out that the cellulose degradation kinetic model in terms of the DP loss accumulation are able to expain the real experimental data of cellulose ageing in mineral oil under different temperature and moisture contents.④Using time-temperature shift factor can calculate the apparent activation energy for kraft paper ageing of in mineral oil, and its value is Ea=(101±15)kJ/mol.⑤Established the oil-paper insulation life prediction model based on time-temperature superposition theory and DP loss accumulation kinetic model. It can applied to assessment DP loss and lifetime of kraft paper ageing in mineral oil under different temperature and moisture contents.